Storage of gas in a canister as a storage container is a common practice. Taking a hydrogen storage canister as an example for explanation, both a hydrogen fuel cell system and an application device powered by hydrogen fuel cells require a proper supply of hydrogen. Hydrogen storage is commonly categorized as pressurized hydrogen, liquid hydrogen, and hydrogen storage alloy, among which pressurized hydrogen is of high energy, high weight, and high density but is also high in volume and poor in safety. Liquid hydrogen is also of high energy, high weight, and high density, but a large consumption of energy is required for liquefaction of hydrogen, and must be stored in a thermal insulation tank. This makes the liquid hydrogen fit for storage in a large-sized tank. For general applications, hydrogen storage alloy is a practical solution, which uses a canister to serve as a storage container for storage of hydrogen.
For both transportation and stationary or portable electrical power supply systems, which are powered by a hydrogen storage canister, replenishment of hydrogen must be made after the hydrogen storage canister runs out of hydrogen storage. This is generally done by exchanging with a fully charged canister at an exchange station. The exchange station then forwards the exhausted canister to a hydrogen supplier for re-charge or alternatively, the exchange station makes on-site re-charge of hydrogen for the exhausted canister.